tyler.durden
/
audk
mirror of https://github.com/acidanthera/audk.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

OvmfPkg/Sec: Add #VC exception handling for Sec phase 

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

An SEV-ES guest will generate a #VC exception when it encounters a
non-automatic exit (NAE) event. It is expected that the #VC exception
handler will communicate with the hypervisor using the GHCB to handle
the NAE event.

NAE events can occur during the Sec phase, so initialize exception
handling early in the OVMF Sec support.

Before establishing the exception handling, validate that the supported
version of the SEV-ES protocol in OVMF is supported by the hypervisor.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Tom Lendacky 2020-08-12 15:21:41 -05:00 committed by mergify[bot]
parent 8a2732186a
commit 13e5492bfd
2 changed files with 173 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

182
OvmfPkg/Sec/SecMain.c
View File

@ -24,6 +24,9 @@
#include <Library/PeCoffExtraActionLib.h>
#include <Library/ExtractGuidedSectionLib.h>
#include <Library/LocalApicLib.h>
#include <Library/CpuExceptionHandlerLib.h>
#include <Register/Amd/Ghcb.h>
#include <Register/Amd/Msr.h>
#include <Ppi/TemporaryRamSupport.h>
@ -34,6 +37,10 @@ typedef struct _SEC_IDT_TABLE {
IA32_IDT_GATE_DESCRIPTOR IdtTable[SEC_IDT_ENTRY_COUNT];
} SEC_IDT_TABLE;
typedef struct _SEC_SEV_ES_WORK_AREA {
UINT8 SevEsEnabled;
} SEC_SEV_ES_WORK_AREA;
VOID
EFIAPI
SecStartupPhase2 (
@ -712,6 +719,120 @@ FindAndReportEntryPoints (
return;
}
/**
Handle an SEV-ES/GHCB protocol check failure.
Notify the hypervisor using the VMGEXIT instruction that the SEV-ES guest
wishes to be terminated.
@param[in] ReasonCode Reason code to provide to the hypervisor for the
termination request.
**/
STATIC
VOID
SevEsProtocolFailure (
IN UINT8 ReasonCode
)
{
MSR_SEV_ES_GHCB_REGISTER Msr;
//
// Use the GHCB MSR Protocol to request termination by the hypervisor
//
Msr.GhcbPhysicalAddress = 0;
Msr.GhcbTerminate.Function = GHCB_INFO_TERMINATE_REQUEST;
Msr.GhcbTerminate.ReasonCodeSet = GHCB_TERMINATE_GHCB;
Msr.GhcbTerminate.ReasonCode = ReasonCode;
AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
AsmVmgExit ();
ASSERT (FALSE);
CpuDeadLoop ();
}
/**
Validate the SEV-ES/GHCB protocol level.
Verify that the level of SEV-ES/GHCB protocol supported by the hypervisor
and the guest intersect. If they don't intersect, request termination.
**/
STATIC
VOID
SevEsProtocolCheck (
VOID
)
{
MSR_SEV_ES_GHCB_REGISTER Msr;
GHCB *Ghcb;
//
// Use the GHCB MSR Protocol to obtain the GHCB SEV-ES Information for
// protocol checking
//
Msr.GhcbPhysicalAddress = 0;
Msr.GhcbInfo.Function = GHCB_INFO_SEV_INFO_GET;
AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
AsmVmgExit ();
Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
if (Msr.GhcbInfo.Function != GHCB_INFO_SEV_INFO) {
SevEsProtocolFailure (GHCB_TERMINATE_GHCB_GENERAL);
}
if (Msr.GhcbProtocol.SevEsProtocolMin > Msr.GhcbProtocol.SevEsProtocolMax) {
SevEsProtocolFailure (GHCB_TERMINATE_GHCB_PROTOCOL);
}
if ((Msr.GhcbProtocol.SevEsProtocolMin > GHCB_VERSION_MAX) ||
(Msr.GhcbProtocol.SevEsProtocolMax < GHCB_VERSION_MIN)) {
SevEsProtocolFailure (GHCB_TERMINATE_GHCB_PROTOCOL);
}
//
// SEV-ES protocol checking succeeded, set the initial GHCB address
//
Msr.GhcbPhysicalAddress = FixedPcdGet32 (PcdOvmfSecGhcbBase);
AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
Ghcb = Msr.Ghcb;
SetMem (Ghcb, sizeof (*Ghcb), 0);
//
// Set the version to the maximum that can be supported
//
Ghcb->ProtocolVersion = MIN (Msr.GhcbProtocol.SevEsProtocolMax, GHCB_VERSION_MAX);
Ghcb->GhcbUsage = GHCB_STANDARD_USAGE;
}
/**
Determine if SEV-ES is active.
During early booting, SEV-ES support code will set a flag to indicate that
SEV-ES is enabled. Return the value of this flag as an indicator that SEV-ES
is enabled.
@retval TRUE SEV-ES is enabled
@retval FALSE SEV-ES is not enabled
**/
STATIC
BOOLEAN
SevEsIsEnabled (
VOID
)
{
SEC_SEV_ES_WORK_AREA *SevEsWorkArea;
SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *) FixedPcdGet32 (PcdSevEsWorkAreaBase);
return ((SevEsWorkArea != NULL) && (SevEsWorkArea->SevEsEnabled != 0));
}
VOID
EFIAPI
SecCoreStartupWithStack (
@ -737,8 +858,56 @@ SecCoreStartupWithStack (
Table[Index] = 0;
}
//
// Initialize IDT - Since this is before library constructors are called,
// we use a loop rather than CopyMem.
//
IdtTableInStack.PeiService = NULL;
for (Index = 0; Index < SEC_IDT_ENTRY_COUNT; Index ++) {
UINT8 *Src;
UINT8 *Dst;
UINTN Byte;
Src = (UINT8 *) &mIdtEntryTemplate;
Dst = (UINT8 *) &IdtTableInStack.IdtTable[Index];
for (Byte = 0; Byte < sizeof (mIdtEntryTemplate); Byte++) {
Dst[Byte] = Src[Byte];
}
}
IdtDescriptor.Base = (UINTN)&IdtTableInStack.IdtTable;
IdtDescriptor.Limit = (UINT16)(sizeof (IdtTableInStack.IdtTable) - 1);
if (SevEsIsEnabled ()) {
SevEsProtocolCheck ();
//
// For SEV-ES guests, the exception handler is needed before calling
// ProcessLibraryConstructorList() because some of the library constructors
// perform some functions that result in #VC exceptions being generated.
//
// Due to this code executing before library constructors, *all* library
// API calls are theoretically interface contract violations. However,
// because this is SEC (executing in flash), those constructors cannot
// write variables with static storage duration anyway. Furthermore, only
// a small, restricted set of APIs, such as AsmWriteIdtr() and
// InitializeCpuExceptionHandlers(), are called, where we require that the
// underlying library not require constructors to have been invoked and
// that the library instance not trigger any #VC exceptions.
//
AsmWriteIdtr (&IdtDescriptor);
InitializeCpuExceptionHandlers (NULL);
}
ProcessLibraryConstructorList (NULL, NULL);
if (!SevEsIsEnabled ()) {
//
// For non SEV-ES guests, just load the IDTR.
//
AsmWriteIdtr (&IdtDescriptor);
}
DEBUG ((DEBUG_INFO,
"SecCoreStartupWithStack(0x%x, 0x%x)\n",
(UINT32)(UINTN)BootFv,
@ -751,19 +920,6 @@ SecCoreStartupWithStack (
//
InitializeFloatingPointUnits ();
//
// Initialize IDT
//
IdtTableInStack.PeiService = NULL;
for (Index = 0; Index < SEC_IDT_ENTRY_COUNT; Index ++) {
CopyMem (&IdtTableInStack.IdtTable[Index], &mIdtEntryTemplate, sizeof (mIdtEntryTemplate));
}
IdtDescriptor.Base = (UINTN)&IdtTableInStack.IdtTable;
IdtDescriptor.Limit = (UINT16)(sizeof (IdtTableInStack.IdtTable) - 1);
AsmWriteIdtr (&IdtDescriptor);
#if defined (MDE_CPU_X64)
//
// ASSERT that the Page Tables were set by the reset vector code to

4
OvmfPkg/Sec/SecMain.inf
View File

@ -50,15 +50,19 @@
PeCoffExtraActionLib
ExtractGuidedSectionLib
LocalApicLib
CpuExceptionHandlerLib
[Ppis]
gEfiTemporaryRamSupportPpiGuid # PPI ALWAYS_PRODUCED
[Pcd]
gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize